rpms/kernel/F-13 virt_console-fix-race.patch, NONE, 1.1 kernel.spec, 1.1943, 1.1944
Kyle McMartin
kyle at fedoraproject.org
Fri Mar 5 12:52:21 UTC 2010
Author: kyle
Update of /cvs/pkgs/rpms/kernel/F-13
In directory cvs1.fedora.phx.redhat.com:/tmp/cvs-serv26244
Modified Files:
kernel.spec
Added Files:
virt_console-fix-race.patch
Log Message:
* Fri Mar 05 2010 Kyle McMartin <kyle at redhat.com>
- Fix race between hvc_close and hvc_remove. (rhbz#568621)
virt_console-fix-race.patch:
hvc_console.c | 31 +++++++++++++++++++++----------
1 file changed, 21 insertions(+), 10 deletions(-)
--- NEW FILE virt_console-fix-race.patch ---
>From patchwork Wed Mar 3 15:29:48 2010
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [v2] hvc_console: Fix race between hvc_close and hvc_remove
Date: Wed, 03 Mar 2010 15:29:48 -0000
From: Amit Shah <amit.shah at redhat.com>
X-Patchwork-Id: 83353
Message-Id: <1267630188-30824-1-git-send-email-amit.shah at redhat.com>
To: linux-kernel at vger.kernel.org
Cc: Amit Shah <amit.shah at redhat.com>, Alan Cox <alan at lxorguk.ukuu.org.uk>,
linuxppc-dev at ozlabs.org, Rusty Russell <rusty at rustcorp.com.au>
Alan pointed out a race in the code where hvc_remove is invoked. The
recent virtio_console work is the first user of hvc_remove().
Alan describes it thus:
The hvc_console assumes that a close and remove call can't occur at the
same time.
In addition tty_hangup(tty) is problematic as tty_hangup is asynchronous
itself....
So this can happen
hvc_close hvc_remove
hung up ? - no
lock
tty = hp->tty
unlock
lock
hp->tty = NULL
unlock
notify del
kref_put the hvc struct
close completes
tty is destroyed
tty_hangup dead tty
tty->ops will be NULL
NULL->...
This patch adds some tty krefs and also converts to using tty_vhangup().
Reported-by: Alan Cox <alan at lxorguk.ukuu.org.uk>
Signed-off-by: Amit Shah <amit.shah at redhat.com>
CC: Alan Cox <alan at lxorguk.ukuu.org.uk>
CC: linuxppc-dev at ozlabs.org
CC: Rusty Russell <rusty at rustcorp.com.au>
---
Alan, how does this version look?
I've tested with multiple virtio_console ports.
There's some other bug in the hvc_remove code that's unrelated:
hot-removal of one console port results in all other hvc consoles to
stop working. I'll look at that once this is finalised.
drivers/char/hvc_console.c | 31 +++++++++++++++++++++----------
1 files changed, 21 insertions(+), 10 deletions(-)
diff --git a/drivers/char/hvc_console.c b/drivers/char/hvc_console.c
index 4c3b59b..7e94b3c 100644
--- a/drivers/char/hvc_console.c
+++ b/drivers/char/hvc_console.c
@@ -312,6 +312,7 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
spin_lock_irqsave(&hp->lock, flags);
/* Check and then increment for fast path open. */
if (hp->count++ > 0) {
+ tty_kref_get(tty);
spin_unlock_irqrestore(&hp->lock, flags);
hvc_kick();
return 0;
@@ -319,7 +320,7 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
tty->driver_data = hp;
- hp->tty = tty;
+ hp->tty = tty_kref_get(tty);
spin_unlock_irqrestore(&hp->lock, flags);
@@ -336,6 +337,7 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
spin_lock_irqsave(&hp->lock, flags);
hp->tty = NULL;
spin_unlock_irqrestore(&hp->lock, flags);
+ tty_kref_put(tty);
tty->driver_data = NULL;
kref_put(&hp->kref, destroy_hvc_struct);
printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc);
@@ -363,13 +365,18 @@ static void hvc_close(struct tty_struct *tty, struct file * filp)
return;
hp = tty->driver_data;
+
spin_lock_irqsave(&hp->lock, flags);
+ tty_kref_get(tty);
if (--hp->count == 0) {
/* We are done with the tty pointer now. */
hp->tty = NULL;
spin_unlock_irqrestore(&hp->lock, flags);
+ /* Put the ref obtained in hvc_open() */
+ tty_kref_put(tty);
+
if (hp->ops->notifier_del)
hp->ops->notifier_del(hp, hp->data);
@@ -389,6 +396,7 @@ static void hvc_close(struct tty_struct *tty, struct file * filp)
spin_unlock_irqrestore(&hp->lock, flags);
}
+ tty_kref_put(tty);
kref_put(&hp->kref, destroy_hvc_struct);
}
@@ -424,10 +432,11 @@ static void hvc_hangup(struct tty_struct *tty)
spin_unlock_irqrestore(&hp->lock, flags);
if (hp->ops->notifier_hangup)
- hp->ops->notifier_hangup(hp, hp->data);
+ hp->ops->notifier_hangup(hp, hp->data);
while(temp_open_count) {
--temp_open_count;
+ tty_kref_put(tty);
kref_put(&hp->kref, destroy_hvc_struct);
}
}
@@ -592,7 +601,7 @@ int hvc_poll(struct hvc_struct *hp)
}
/* No tty attached, just skip */
- tty = hp->tty;
+ tty = tty_kref_get(hp->tty);
if (tty == NULL)
goto bail;
@@ -672,6 +681,8 @@ int hvc_poll(struct hvc_struct *hp)
tty_flip_buffer_push(tty);
}
+ if (tty)
+ tty_kref_put(tty);
return poll_mask;
}
@@ -807,7 +818,7 @@ int hvc_remove(struct hvc_struct *hp)
struct tty_struct *tty;
spin_lock_irqsave(&hp->lock, flags);
- tty = hp->tty;
+ tty = tty_kref_get(hp->tty);
if (hp->index < MAX_NR_HVC_CONSOLES)
vtermnos[hp->index] = -1;
@@ -819,18 +830,18 @@ int hvc_remove(struct hvc_struct *hp)
/*
* We 'put' the instance that was grabbed when the kref instance
* was initialized using kref_init(). Let the last holder of this
- * kref cause it to be removed, which will probably be the tty_hangup
+ * kref cause it to be removed, which will probably be the tty_vhangup
* below.
*/
kref_put(&hp->kref, destroy_hvc_struct);
/*
- * This function call will auto chain call hvc_hangup. The tty should
- * always be valid at this time unless a simultaneous tty close already
- * cleaned up the hvc_struct.
+ * This function call will auto chain call hvc_hangup.
*/
- if (tty)
- tty_hangup(tty);
+ if (tty) {
+ tty_vhangup(tty);
+ tty_kref_put(tty);
+ }
return 0;
}
EXPORT_SYMBOL_GPL(hvc_remove);
Index: kernel.spec
===================================================================
RCS file: /cvs/pkgs/rpms/kernel/F-13/kernel.spec,v
retrieving revision 1.1943
retrieving revision 1.1944
diff -u -p -r1.1943 -r1.1944
--- kernel.spec 5 Mar 2010 01:51:47 -0000 1.1943
+++ kernel.spec 5 Mar 2010 12:52:20 -0000 1.1944
@@ -682,6 +682,7 @@ Patch1551: linux-2.6-ksm-kvm.patch
Patch1552: linux-2.6-userspace_kvmclock_offset.patch
Patch1553: vhost_net-rollup.patch
Patch1554: virt_console-rollup.patch
+Patch1555: virt_console-fix-race.patch
# fbdev x86-64 primary fix
Patch1700: linux-2.6-x86-64-fbdev-primary.patch
@@ -1301,6 +1302,7 @@ ApplyPatch crystalhd-2.6.34-staging.patc
#ApplyPatch linux-2.6-userspace_kvmclock_offset.patch
ApplyPatch vhost_net-rollup.patch
ApplyPatch virt_console-rollup.patch
+ApplyPatch virt_console-fix-race.patch
# Fix block I/O errors in KVM
#ApplyPatch linux-2.6-block-silently-error-unsupported-empty-barriers-too.patch
@@ -1994,6 +1996,9 @@ fi
# and build.
%changelog
+* Fri Mar 05 2010 Kyle McMartin <kyle at redhat.com>
+- Fix race between hvc_close and hvc_remove. (rhbz#568621)
+
* Thu Mar 04 2010 Kyle McMartin <kyle at redhat.com>
- Enable CGROUP_DEBUG.
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